Thank-you for your intelligent comments. See, you did some research (or knew NFS already). I don't agree that the other guy did any real research. I would also disagree with you about file synchronization. It is an application-layer function. The session layer doesn't know what "a file" is.
The materials that you see that assign NFS to the wrong layer are just copy and paste errors. It just takes common sense to see that. A lot of the course developers at Cisco were not very technical. They didn't understand layering, protocol analysis, etc., and had probably never heard of RPC. For a while the Cisco training department hired education majors instead of engineers or network administrators. That's why you see so much effort put into the Objectives slides and so many mistakes when you get into the meat. ;-) While I respect the Packet magazine, it's important to realize it's a marketing magazine. Also, the author of this particular article has a CCNA and CCDA. So, we know what sources he used. (the wrong ones) If you want to read a good (academic and engineering-focused) magazine from Cisco, try the Internet Protocol Journal. They wouldn't make such a mistake (hopefully!?) ;-) Peace, Priscilla At 04:59 PM 12/9/01, Carroll Kong wrote: >Priscilla, I think you are being a bit too hard on the guy. He >tried to do some real research, he is referencing other written >material. I did some quick research and I am finding some information is >clashing about it. I think sometimes it is hard to make the differentiate >between the layers for certain constructs. > I think perhaps, WHY NFS is so often put in the Session Layer is >because it uses RPC. Also, NFS does do synchronization of files, which can >be heavily argued as a Session Layer characteristic. I would say RPC >definitely is in the Session Layer. NFS does synchronization, (remember >the ancient days of keeping file consistency with UDP?) but looks like it >might be at the application layer. I suppose that is where the confusion >is. And since NFS definitely uses RPC, and there "can only be ONE", >perhaps NFS is truly just at the application layer. You could argue that >it mountd that really allows remote mounting and nfsd just does >synchronization. > I think it is somewhat debatable and reasonable for him to think >otherwise if so many other references point it to the wrong direction. > I am interested in any reference, as that is how we make sure we >did not mislearn something. > >At 02:04 PM 12/9/01 -0500, Priscilla Oppenheimer wrote: > >At 06:18 PM 12/8/01, anil wrote: > > >This is from Cisco Oct 2001 Packet.. > > >http://www.cisco.com/warp/public/784/packet/oct01/p76-training.html > > > > > >It must be out of date :-) > > > >Not "out of date." Just wrong. You can keep coming up with wrong material. > >What's your point? > > > >Have you looked at NFS with a Sniffer? Have you read a Unix man page? Have > >you checked some RFCs? > > > >Have you considered what NFS does? What are its functions? What do its > >messages look like? What protocols below it does it rely on? What problems > >were its creators trying to solve? > > > >Please stop sending messages about this topic (or any other topic) until > >you have done some real research. In your last message you quoted page 9 of > >a CCNA book. Sorry to burst your bubble, but nobody on this list could care > >less what it says on page 9 of a CCNA book. This list is for people > >studying for advanced Cisco certifications. > > > >Priscilla > > > > >-Anil > > >------------------------ > > > > > >5. Session Layer > > >The session layer provides services in the application to manage >inter-host > > >communication. Think of this function as the old-time telephone >switchboard > > >operator: first, watching for a light on the switchboard indicating a > > >connection was needed, next connecting and monitoring the call, and then > > >finally disconnecting it by pulling the plug. For example, Network File > > >System (NFS) is like an extended feature Telnet program for UNIX that >keeps > > >a connection (session) alive and available until the terminate command is > > >given. Other examples include Structured Query Language (SQL), Remote > > >Procedure Call (RPC), and X-Windows. > > > > > > > > >-----Original Message----- > > >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > >Priscilla Oppenheimer > > >Sent: Saturday, December 08, 2001 3:13 AM > > >To: [EMAIL PROTECTED] > > >Subject: RE: Does session layer protocol use IP address ? [7:28378] > > > > > > > > >That's 40% right. > > > > > >SQL, NFS, and XWindows are application-layer protocols. > > > > > >RPC and NetBIOS are session-layer protocols. > > > > > >We often have discussions about which books are best. Todd Lammle books >can > > >teach you basic router configuration. They are often wrong where protocol > > >behavior is concerned. > > > > > >A better reference for learning about OSI is the OSI paper by Howard > > >Berkowitz at http://www.certificationzone.com. > > > > > >Priscilla > > > > > >At 11:32 PM 12/7/01, anil wrote: > > > > >The session layer is an elusive beast that is not implemented much > > > >Yes, I checked it out.. > > > >Session layer protocols include: > > > >SQL, NFS, RPC, NetBios, Xwindows are examples of session layer >protocols. > > > >Page 9 of CCNA 2nd Edition study guide Todd Lammle > > > > > > > >-Anil > > > > > > > > > > > > > > > > > > > >-----Original Message----- > > > >From: anil [mailto:[EMAIL PROTECTED]] > > > >Sent: Friday, December 07, 2001 11:17 PM > > > >To: Priscilla Oppenheimer; [EMAIL PROTECTED] > > > >Subject: RE: Does session layer protocol use IP address ? [7:28378] > > > > > > > > > > > > >The session layer is an elusive beast that is not implemented much > > > >Wait a sec, I thought SQL, NFS and netbios were session layer protocols? > > > >Someone please correct me. > > > >-Anil > > > > > > > > > > > >-----Original Message----- > > > >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > > >Priscilla Oppenheimer > > > >Sent: Friday, December 07, 2001 9:55 PM > > > >To: [EMAIL PROTECTED] > > > >Subject: Re: Does session layer protocol use IP address ? [7:28378] > > > > > > > > > > > >At 02:59 AM 12/7/01, mlh wrote: > > > > >Hi, there, > > > > > > > > > >I read Todd Lammle's CCNA2.0 study guide and found this sentence: > > >"Remember > > > > >that none of the upper > > > > >layers know anything about networking or network addresses." I am > > >wondering > > > > >if the session layer doesn't > > > > >use network address, how can it establish a dialogue with other >session > > > > >layer in other host? > > > > > > > >I would probably disagree with Todd's statement, although it's taken out > >of > > > >context and you haven't given us enough information to say that the > > > >statement is definitely "wrong." > > > > > > > >However, try to picture the numerous OSI pictures you have seen. Most of > > > >them show horizontal lines between a layer on one host talking to the >same > > > >layer on another host. So the session layer talks to the session layer >on > > > >the other host. That's probably what Todd was getting at. > > > > > > > >However, the pictures also show vertical lines. A layer calls on a layer > > > >below to provide services. Each layer offers services to layers above >it. > > > > > > > >The session layer is an elusive beast that is not implemented much. But > >one > > > >example might help. NetBIOS is a session layer. On a Windows client, >when > > > >you access a Server Message Block (SMB) server, NetBIOS has the job of > > > >setting up a session with the server. Before it can do that, however, it > > > >must find the address of the server. If it's a modern Windows network, > >then > > > >SMB and NetBIOS are probably running above TCP/IP and UDP/IP. So NetBIOS > > > >sends a DNS or WINS query to find the IP address of the named server. It > > > >then sets up a NetBIOS session with the server. Actually, first, the > >client > > > >sets up a TCP connection. TCP has port numbers. The client sends to the > > > >well-known TCP port for NetBIOS session (139) and use an ephemeral port >on > > > >its side. These port numbers could be considered "addresses" at the > > > >transport layer. > > > > > > > >Anyway, back to the question. The statement is at best over-simplified. >I > > > >recommend you get yourself a sniffer and watch what really happens >between > > > >layers. (Ethereal is free by the way.) > > > > > > > >Priscilla > > > > > > > > > > > > > > > > >Thank you for your time. > > > > > > > > > >mlh > > > >________________________ > > > > > > > >Priscilla Oppenheimer > > > >http://www.priscilla.com > > >________________________ > > > > > >Priscilla Oppenheimer > > >http://www.priscilla.com > >________________________ > > > >Priscilla Oppenheimer > >http://www.priscilla.com >-Carroll Kong ________________________ Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=28775&t=28378 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
